Let pret-lam support blocks of multiple lambda expressions.

This enables subscript detection from one lambda expression or buffer to
influence the lambda detection in other buffer.

diff --git a/pret-lam.lua b/pret-lam.lua
index ce4ac4719696cbdc74add9f36875f2b463b9a1a3..2e70001aa90ff6971f7ff89c946a2f390a22b0ba 100644 (file)
--- a/pret-lam.lua
+++ b/pret-lam.lua
@@ -101,14 +101,38 @@ local function do_subscripts(word)
     return word
 end
 
+local in_block = 0
+
+-- Mark the begin of a block of lambda formatted buffers or expressions. This
+-- means that, until you call end_of_block again, the subscript bases are
+-- shared. For example, if you have \lam{y1} some text \lam{yn} within a
+-- single block, the yn will properly get subscripted. Be sure to call
+-- end_of_block again!
+--
+-- Blocks can be partially nested, meaning that the block
+-- won't be closed until end_of_block was called exactly as often as
+-- begin_of_block. However, subscripts from the inner block can still
+-- influence subscripts in the outer block.
+function vis.begin_of_block()
+    vis.begin_of_display()
+    in_block = in_block + 1
+end
+
+-- Ends the current block
+function vis.end_of_block()
+    in_block = in_block - 1
+end
+
 function vis.begin_of_display()
-    -- Initially allow subscripts using _ or just appending a number (later,
-    -- we will add extra patterns here.
-    submatches = {"^(%a*)_([%a%d,]+)$", "^(%a+)(%d+)$"}
-    -- This stores all the bases we've encountered so far (to prevent
-    -- duplicates). For each of them there will be a pattern in submatches
-    -- above.
-    bases = {}
+    if in_block == 0 then
+        -- Initially allow subscripts using _ or just appending a number (later,
+        -- we will add extra patterns here.
+        submatches = {"^(%a*)_([%a%d,]+)$", "^(%a+)(%d+)$"}
+        -- This stores all the bases we've encountered so far (to prevent
+        -- duplicates). For each of them there will be a pattern in submatches
+        -- above.
+        bases = {}
+    end
 end
 
 -- Make things work for inline typeing (e.g., \type{}) as well.