2010-05-25 A lemma about substitution in TypeSchemes.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 25 May 2010 17:09:29 +0200] rev 2179
A lemma about substitution in TypeSchemes.
2010-05-25 reversing the direction of fresh_star
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 25 May 2010 17:01:37 +0200] rev 2178
reversing the direction of fresh_star
2010-05-25 overlapping deep binders proof
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 25 May 2010 10:43:19 +0200] rev 2177
overlapping deep binders proof
2010-05-25 edits from the reviewers
Christian Urban <urbanc@in.tum.de> [Tue, 25 May 2010 07:59:16 +0200] rev 2176
edits from the reviewers
2010-05-24 tuned paper
Christian Urban <urbanc@in.tum.de> [Mon, 24 May 2010 22:47:06 +0100] rev 2175
tuned paper
2010-05-23 changed qpaper to lncs-style
Christian Urban <urbanc@in.tum.de> [Sun, 23 May 2010 16:45:00 +0100] rev 2174
changed qpaper to lncs-style
2010-05-21 Match_Lam defined on Quotient Level.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 17:17:51 +0200] rev 2173
Match_Lam defined on Quotient Level.
2010-05-21 More on Function-defined subst.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 11:55:22 +0200] rev 2172
More on Function-defined subst.
2010-05-21 Isabelle renamings
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 11:46:47 +0200] rev 2171
Isabelle renamings
2010-05-21 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 10:47:45 +0200] rev 2170
merge
2010-05-21 Renamings.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 10:43:14 +0200] rev 2169
Renamings.
2010-05-21 Renamings
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 10:42:53 +0200] rev 2168
Renamings
2010-05-21 merge (non-trival)
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 10:47:07 +0200] rev 2167
merge (non-trival)
2010-05-21 Previously uncommited direct subst definition changes.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 10:45:29 +0200] rev 2166
Previously uncommited direct subst definition changes.
2010-05-21 Function experiments
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 21 May 2010 10:44:07 +0200] rev 2165
Function experiments
2010-05-19 merged
Christian Urban <urbanc@in.tum.de> [Wed, 19 May 2010 12:44:03 +0100] rev 2164
merged
2010-05-19 added comments about pottiers work
Christian Urban <urbanc@in.tum.de> [Wed, 19 May 2010 12:43:38 +0100] rev 2163
added comments about pottiers work
2010-05-19 more subst experiments
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 19 May 2010 12:29:08 +0200] rev 2162
more subst experiments
2010-05-19 More subst experminets
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 19 May 2010 11:29:42 +0200] rev 2161
More subst experminets
2010-05-18 more on subst
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 17:56:41 +0200] rev 2160
more on subst
2010-05-18 Single variable substitution
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 17:17:54 +0200] rev 2159
Single variable substitution
2010-05-18 subst fix
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 17:06:21 +0200] rev 2158
subst fix
2010-05-18 subst experiments
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 15:58:52 +0200] rev 2157
subst experiments
2010-05-18 soem minor tuning
Christian Urban <urbanc@in.tum.de> [Tue, 18 May 2010 14:40:05 +0100] rev 2156
soem minor tuning
2010-05-18 Fix broken add
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 11:47:29 +0200] rev 2155
Fix broken add
2010-05-18 add missing .bib
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 11:46:58 +0200] rev 2154
add missing .bib
2010-05-18 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 11:46:19 +0200] rev 2153
merge
2010-05-18 starting bibliography
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 18 May 2010 11:45:49 +0200] rev 2152
starting bibliography
2010-05-17 merged
Christian Urban <urbanc@in.tum.de> [Mon, 17 May 2010 20:23:40 +0100] rev 2151
merged
2010-05-17 updated to new Isabelle (More_Conv -> Conv)
Christian Urban <urbanc@in.tum.de> [Mon, 17 May 2010 18:13:39 +0100] rev 2150
updated to new Isabelle (More_Conv -> Conv)
2010-05-17 made this example to work again
Christian Urban <urbanc@in.tum.de> [Mon, 17 May 2010 17:54:07 +0100] rev 2149
made this example to work again
2010-05-17 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 17 May 2010 17:34:02 +0200] rev 2148
merge
2010-05-17 alpha_alphabn for bindings in a type under bn.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 17 May 2010 17:31:18 +0200] rev 2147
alpha_alphabn for bindings in a type under bn.
2010-05-17 minor tuning
Christian Urban <urbanc@in.tum.de> [Mon, 17 May 2010 16:25:45 +0100] rev 2146
minor tuning
2010-05-17 Ex4 does work, and I don't see the difference between the alphas.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 17 May 2010 16:29:33 +0200] rev 2145
Ex4 does work, and I don't see the difference between the alphas.
2010-05-17 slight tuning
Christian Urban <urbanc@in.tum.de> [Mon, 17 May 2010 12:46:51 +0100] rev 2144
slight tuning
2010-05-17 somewhat simplified the main parsing function; failed to move a Note-statement to define_raw_perms
Christian Urban <urbanc@in.tum.de> [Mon, 17 May 2010 12:00:54 +0100] rev 2143
somewhat simplified the main parsing function; failed to move a Note-statement to define_raw_perms
2010-05-16 moved the exporting part into the parser (this is still a hack); re-added CoreHaskell again to the examples - there seems to be a problem with the variable name pat
Christian Urban <urbanc@in.tum.de> [Sun, 16 May 2010 12:41:27 +0100] rev 2142
moved the exporting part into the parser (this is still a hack); re-added CoreHaskell again to the examples - there seems to be a problem with the variable name pat
2010-05-16 tuned paper
Christian Urban <urbanc@in.tum.de> [Sun, 16 May 2010 11:00:44 +0100] rev 2141
tuned paper
2010-05-15 tuned paper
Christian Urban <urbanc@in.tum.de> [Sat, 15 May 2010 22:06:06 +0100] rev 2140
tuned paper
2010-05-14 tuned a bit the paper
Christian Urban <urbanc@in.tum.de> [Fri, 14 May 2010 21:18:34 +0100] rev 2139
tuned a bit the paper
2010-05-14 started a new file for the parser to make some experiments
Christian Urban <urbanc@in.tum.de> [Fri, 14 May 2010 18:12:07 +0100] rev 2138
started a new file for the parser to make some experiments
2010-05-14 moved old parser and fv into attic
Christian Urban <urbanc@in.tum.de> [Fri, 14 May 2010 17:58:26 +0100] rev 2137
moved old parser and fv into attic
2010-05-14 polished example
Christian Urban <urbanc@in.tum.de> [Fri, 14 May 2010 17:40:43 +0100] rev 2136
polished example
2010-05-14 merged
Christian Urban <urbanc@in.tum.de> [Fri, 14 May 2010 15:21:05 +0100] rev 2135
merged
2010-05-14 tuned a bit the paper
Christian Urban <urbanc@in.tum.de> [Fri, 14 May 2010 15:02:25 +0100] rev 2134
tuned a bit the paper
2010-05-14 Proper fv/alpha for multiple compound binders
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 14 May 2010 15:37:23 +0200] rev 2133
Proper fv/alpha for multiple compound binders
2010-05-14 SingleLetFoo with everything.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 14 May 2010 10:28:42 +0200] rev 2132
SingleLetFoo with everything.
2010-05-14 Fv for multiple binding functions
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 14 May 2010 10:21:14 +0200] rev 2131
Fv for multiple binding functions
2010-05-13 added a more instructive example - has some problems with fv though
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 19:06:54 +0100] rev 2130
added a more instructive example - has some problems with fv though
2010-05-13 added flip_eqvt and swap_eqvt to the equivariance lists
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 18:19:48 +0100] rev 2129
added flip_eqvt and swap_eqvt to the equivariance lists
2010-05-13 tuned the paper
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 17:41:28 +0100] rev 2128
tuned the paper
2010-05-13 properly declared outer keyword
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 16:09:34 +0100] rev 2127
properly declared outer keyword
2010-05-13 added an example which goes outside our current speciifcation
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 15:58:36 +0100] rev 2126
added an example which goes outside our current speciifcation
2010-05-13 made out of STEPS a configuration value so that it can be set individually in each file
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 15:58:02 +0100] rev 2125
made out of STEPS a configuration value so that it can be set individually in each file
2010-05-13 tuned eqvt-proofs about prod_rel and prod_fv
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 15:12:34 +0100] rev 2124
tuned eqvt-proofs about prod_rel and prod_fv
2010-05-13 removed internal functions from the signature (they are not needed anymore)
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 15:12:05 +0100] rev 2123
removed internal functions from the signature (they are not needed anymore)
2010-05-13 added term4 back to the examples
Christian Urban <urbanc@in.tum.de> [Thu, 13 May 2010 10:34:59 +0100] rev 2122
added term4 back to the examples
2010-05-13 Make Term4 use 'equivariance'.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 13 May 2010 07:41:18 +0200] rev 2121
Make Term4 use 'equivariance'.
2010-05-12 fixed the examples for the new eqvt-procedure....temporarily disabled Manual/Term4.thy
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 16:59:53 +0100] rev 2120
fixed the examples for the new eqvt-procedure....temporarily disabled Manual/Term4.thy
2010-05-12 merged
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 16:33:50 +0100] rev 2119
merged
2010-05-12 moved the data-transformation into the parser
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 16:33:25 +0100] rev 2118
moved the data-transformation into the parser
2010-05-12 added a test whether some of the constants already equivariant (then the procedure has to fail).
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 16:26:06 +0100] rev 2117
added a test whether some of the constants already equivariant (then the procedure has to fail).
2010-05-12 include set_simps and append_simps in fv_rsp
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:57:01 +0200] rev 2116
include set_simps and append_simps in fv_rsp
2010-05-12 Move alpha_eqvt to unused.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:39:10 +0200] rev 2115
Move alpha_eqvt to unused.
2010-05-12 Use equivariance instead of alpha_eqvt
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:32:44 +0200] rev 2114
Use equivariance instead of alpha_eqvt
2010-05-12 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:18:04 +0200] rev 2113
merge
2010-05-12 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:11:23 +0200] rev 2112
merge
2010-05-12 fvbv_rsp include prod_rel.simps
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:11:03 +0200] rev 2111
fvbv_rsp include prod_rel.simps
2010-05-12 better ML-interface (returning only a list of theorems and a context)
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 15:17:35 +0100] rev 2110
better ML-interface (returning only a list of theorems and a context)
2010-05-12 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:09:38 +0200] rev 2109
merge
2010-05-12 Use raw_induct instead of induct
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 12 May 2010 16:08:32 +0200] rev 2108
Use raw_induct instead of induct
2010-05-12 ingnored parameters in equivariance; added a proper interface to be called from ML
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 14:47:52 +0100] rev 2107
ingnored parameters in equivariance; added a proper interface to be called from ML
2010-05-12 properly exported defined bn-functions
Christian Urban <urbanc@in.tum.de> [Wed, 12 May 2010 13:43:48 +0100] rev 2106
properly exported defined bn-functions
2010-05-11 Include raw permutation definitions in eqvt
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 11 May 2010 18:20:25 +0200] rev 2105
Include raw permutation definitions in eqvt
2010-05-11 Declare alpha_gen_eqvt as eqvt and change the proofs that used 'eqvts[symmetric]'
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 11 May 2010 17:16:57 +0200] rev 2104
Declare alpha_gen_eqvt as eqvt and change the proofs that used 'eqvts[symmetric]'
2010-05-11 a bit for the introduction of the q-paper
Christian Urban <urbanc@in.tum.de> [Tue, 11 May 2010 14:58:46 +0100] rev 2103
a bit for the introduction of the q-paper
2010-05-11 added some of the quotient literature; a bit more to the qpaper
Christian Urban <urbanc@in.tum.de> [Tue, 11 May 2010 12:18:26 +0100] rev 2102
added some of the quotient literature; a bit more to the qpaper
2010-05-10 fixed a problem with non-existant alphas2
Christian Urban <urbanc@in.tum.de> [Mon, 10 May 2010 18:09:00 +0100] rev 2101
fixed a problem with non-existant alphas2
2010-05-10 added comment about bind_set
Christian Urban <urbanc@in.tum.de> [Mon, 10 May 2010 17:57:22 +0100] rev 2100
added comment about bind_set
2010-05-10 fixing bind_set problem
Christian Urban <urbanc@in.tum.de> [Mon, 10 May 2010 17:55:54 +0100] rev 2099
fixing bind_set problem
2010-05-10 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 18:32:50 +0200] rev 2098
merge
2010-05-10 Term8 comment
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 18:32:15 +0200] rev 2097
Term8 comment
2010-05-10 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 18:30:27 +0200] rev 2096
merge
2010-05-10 Restore set bindings in CoreHaskell
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 18:29:45 +0200] rev 2095
Restore set bindings in CoreHaskell
2010-05-10 Recursive examples with relation composition
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:54:16 +0200] rev 2094
Recursive examples with relation composition
2010-05-10 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:45:04 +0200] rev 2093
merge
2010-05-10 prod_rel and prod_fv eqvt and mono
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:44:49 +0200] rev 2092
prod_rel and prod_fv eqvt and mono
2010-05-10 ExLetRec
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:14:02 +0200] rev 2091
ExLetRec
2010-05-10 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:11:19 +0200] rev 2090
merge
2010-05-10 Parser changes for compound relations
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:11:05 +0200] rev 2089
Parser changes for compound relations
2010-05-10 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:09:53 +0200] rev 2088
merge
2010-05-10 Use mk_compound_fv' and mk_compound_rel'
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 15:09:32 +0200] rev 2087
Use mk_compound_fv' and mk_compound_rel'
2010-05-10 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 12:05:13 +0200] rev 2086
merge
2010-05-10 Membership in a pair of lists.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 12:04:40 +0200] rev 2085
Membership in a pair of lists.
2010-05-10 Synchronize FSet with repository
Cezary Kaliszyk <kaliszyk@in.tum.de> [Mon, 10 May 2010 10:22:57 +0200] rev 2084
Synchronize FSet with repository
2010-05-09 tuned file names for examples
Christian Urban <urbanc@in.tum.de> [Sun, 09 May 2010 12:38:59 +0100] rev 2083
tuned file names for examples
2010-05-09 cleaned up a bit the examples; added equivariance to all examples
Christian Urban <urbanc@in.tum.de> [Sun, 09 May 2010 12:26:10 +0100] rev 2082
cleaned up a bit the examples; added equivariance to all examples
2010-05-09 fixed the problem with alpha containing splits
Christian Urban <urbanc@in.tum.de> [Sun, 09 May 2010 11:43:24 +0100] rev 2081
fixed the problem with alpha containing splits
2010-05-09 added eqvt-lemma for split; changed semantics of perm_simp: excluded stands for constants about which no complaint is written out...eqvt_apply is now always applied
Christian Urban <urbanc@in.tum.de> [Sun, 09 May 2010 11:37:19 +0100] rev 2080
added eqvt-lemma for split; changed semantics of perm_simp: excluded stands for constants about which no complaint is written out...eqvt_apply is now always applied
2010-05-07 Manually added some newer keywords from the distribution
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 07 May 2010 12:28:11 +0200] rev 2079
Manually added some newer keywords from the distribution
2010-05-07 Regularize experiments
Cezary Kaliszyk <kaliszyk@in.tum.de> [Fri, 07 May 2010 12:10:04 +0200] rev 2078
Regularize experiments
2010-05-06 alpha_eqvt_tac with prod_rel and prod_fv simps
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:21:10 +0200] rev 2077
alpha_eqvt_tac with prod_rel and prod_fv simps
2010-05-06 mem => member
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:14:30 +0200] rev 2076
mem => member
2010-05-06 merge
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:13:45 +0200] rev 2075
merge
2010-05-06 Fixes for new Isabelle
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:13:35 +0200] rev 2074
Fixes for new Isabelle
2010-05-06 compound versions with prod_rel and prod_fun, not made default yet.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:13:05 +0200] rev 2073
compound versions with prod_rel and prod_fun, not made default yet.
2010-05-06 prod_rel and prod_fv simps
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:10:56 +0200] rev 2072
prod_rel and prod_fv simps
2010-05-06 mem => member
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:10:26 +0200] rev 2071
mem => member
2010-05-06 prod_rel.simps and Fixed for new isabelle
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:09:56 +0200] rev 2070
prod_rel.simps and Fixed for new isabelle
2010-05-06 Fixes for new isabelle
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 14:09:21 +0200] rev 2069
Fixes for new isabelle
2010-05-06 prod_fv and its respectfullness and preservation.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 13:25:37 +0200] rev 2068
prod_fv and its respectfullness and preservation.
2010-05-06 Experiments with equivariance.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Thu, 06 May 2010 10:43:41 +0200] rev 2067
Experiments with equivariance.
2010-05-05 merged
Christian Urban <urbanc@in.tum.de> [Wed, 05 May 2010 20:39:56 +0100] rev 2066
merged
2010-05-05 a bit mor on the pearl journal paper
Christian Urban <urbanc@in.tum.de> [Wed, 05 May 2010 20:39:21 +0100] rev 2065
a bit mor on the pearl journal paper
2010-05-05 solved the problem with equivariance by first eta-normalising the goal
Christian Urban <urbanc@in.tum.de> [Wed, 05 May 2010 10:24:54 +0100] rev 2064
solved the problem with equivariance by first eta-normalising the goal
2010-05-05 Some cleaning in Term4
Cezary Kaliszyk <kaliszyk@in.tum.de> [Wed, 05 May 2010 09:23:10 +0200] rev 2063
Some cleaning in Term4
2010-05-04 "isabelle make" compiles all examples with newparser/newfv/newalpha only.
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 04 May 2010 17:25:58 +0200] rev 2062
"isabelle make" compiles all examples with newparser/newfv/newalpha only.
2010-05-04 Move Term4 to NewParser
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 04 May 2010 17:15:21 +0200] rev 2061
Move Term4 to NewParser
2010-05-04 Fix Term4 for permutation signature change
Cezary Kaliszyk <kaliszyk@in.tum.de> [Tue, 04 May 2010 16:59:31 +0200] rev 2060
Fix Term4 for permutation signature change
(0) -1000 -120 +120 +1000 tip