1 files changed, 71 insertions, 0 deletions
diff --git a/runtime/indent/prolog.vim b/runtime/indent/prolog.vim
new file mode 100644
index 0000000..0c4fd54
--- /dev/null
+++ b/runtime/indent/prolog.vim
@@ -0,0 +1,71 @@
+"  vim: set sw=4 sts=4:
+"  Language:	Prolog
+"  Maintainer:	Gergely Kontra <kgergely@mcl.hu> (Invalid email address)
+" 		Doug Kearns <dougkearns@gmail.com>
+"  Revised on:	2002.02.18. 23:34:05
+"  Last change by: Takuya Fujiwara, 2018 Sep 23
+"		2022 April: b:undo_indent added by Doug Kearns
+
+" TODO:
+"   checking with respect to syntax highlighting
+"   ignoring multiline comments
+"   detecting multiline strings
+
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+    finish
+endif
+
+let b:did_indent = 1
+
+setlocal indentexpr=GetPrologIndent()
+setlocal indentkeys-=:,0#
+setlocal indentkeys+=0%,-,0;,>,0)
+
+let b:undo_indent = "setl inde< indk<"
+
+" Only define the function once.
+"if exists("*GetPrologIndent")
+"    finish
+"endif
+
+function! GetPrologIndent()
+    " Find a non-blank line above the current line.
+    let pnum = prevnonblank(v:lnum - 1)
+    " Hit the start of the file, use zero indent.
+    if pnum == 0
+       return 0
+    endif
+    let line = getline(v:lnum)
+    let pline = getline(pnum)
+
+    let ind = indent(pnum)
+    " Previous line was comment -> use previous line's indent
+    if pline =~ '^\s*%'
+	return ind
+    endif
+    " Previous line was the start of block comment -> +1 after '/*' comment
+    if pline =~ '^\s*/\*'
+	return ind + 1
+    endif
+    " Previous line was the end of block comment -> -1 after '*/' comment
+    if pline =~ '^\s*\*/'
+	return ind - 1
+    endif
+    " Check for clause head on previous line
+    if pline =~ '\%(:-\|-->\)\s*\(%.*\)\?$'
+	let ind = ind + shiftwidth()
+    " Check for end of clause on previous line
+    elseif pline =~ '\.\s*\(%.*\)\?$'
+	let ind = ind - shiftwidth()
+    endif
+    " Check for opening conditional on previous line
+    if pline =~ '^\s*\([(;]\|->\)'
+	let ind = ind + shiftwidth()
+    endif
+    " Check for closing an unclosed paren, or middle ; or ->
+    if line =~ '^\s*\([);]\|->\)'
+	let ind = ind - shiftwidth()
+    endif
+    return ind
+endfunction