From b6c45648033e3e6d5ad85178b43a57d4aa8bab43 Mon Sep 17 00:00:00 2001 From: Marshall Lochbaum Date: Mon, 18 Jan 2021 20:06:55 -0500 Subject: Mention Roger's discussion of hook as a conjunction, not a train --- commentary/history.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'commentary') diff --git a/commentary/history.md b/commentary/history.md index b37d81eb..5963d19f 100644 --- a/commentary/history.md +++ b/commentary/history.md @@ -81,7 +81,7 @@ I've been fiddling with the idea of function or map inversion (preimage creation #### Before `⊸` and After `⟜` -It happens that BQN's Before (`⊸`) and After (`⟜`) modifiers are identical to I's hook (`h`) and backhook (`H`), but it took some time to arrive at this point. The hook function in I comes from J's 2-train, also called hook. But the model for Before and After was initially APL's Compose (∘) and the complement [Reverse Compose](https://aplwiki.com/wiki/Reverse_Compose) that Adám created for Extended Dyalog APL. I noticed the similarity to Bind and decided to unify Binds and Composes at around the same time that I picked the symbols `⊸⟜`. However, I kept the idea that the one-argument case should be simple composition unless the bound operand had a subject role. Eventually I decided the violation of [syntactic type erasure](problems.md#syntactic-type-erasure) was too inconsistent and settled on the current definition. Now I think these forms are better even ignoring constant functions, although I do occasionally run into cases where I'd like to use APL's Compose. +It happens that BQN's Before (`⊸`) and After (`⟜`) modifiers are identical to I's hook (`h`) and backhook (`H`), but it took some time to arrive at this point. The hook function in I comes from J's 2-train, also called hook (I had probably seen Roger Hui's [remarks](https://code.jsoftware.com/wiki/Essays/Hook_Conjunction%3F) that he would prefer hook to be a conjunction, with 2-trains indicating composition instead, but I don't think Roger has proposed a reverse hook). But the model for Before and After was initially APL's Compose (`∘`) and the complement [Reverse Compose](https://aplwiki.com/wiki/Reverse_Compose) that Adám created for Extended Dyalog APL. I noticed the similarity to Bind and decided to unify Binds and Composes at around the same time that I picked the symbols `⊸⟜`. However, I kept the idea that the one-argument case should be simple composition unless the bound operand had a subject role. Eventually I decided the violation of [syntactic type erasure](problems.md#syntactic-type-erasure) was too inconsistent and settled on the current definition. Now I think these forms are better even ignoring constant functions, although I do occasionally run into cases where I'd like to use APL's Compose. #### Constant modifier -- cgit v1.2.3