stdlib: Implement filter() and filter-out() functions.

[goals.git] / stdlib / prelude.gl

diff --git a/stdlib/prelude.gl b/stdlib/prelude.gl
index 7dc3b73..d8e523a 100644 (file)
--- a/stdlib/prelude.gl
+++ b/stdlib/prelude.gl
@@ -59,6 +59,16 @@ pure function wrap (wrapper, xs) = @{
 #----------------------------------------------------------------------
 # Text functions.
 
+# Filter a list by regexp.
+pure function filter (pat, xs) returning strings = @{
+    for f in %xs; do echo "$f"; done | grep -E -- %pat
+}
+
+# Filter out a list by regexp.
+pure function filter-out (pat, xs) returning strings = @{
+    for f in %xs; do echo "$f"; done | grep -v -E -- %pat
+}
+
 # Head of a list.
 pure function head (xs) returning string = @{
     for f in %xs; do
@@ -98,12 +108,12 @@ pure function tail (xs) returning strings = @{
 
 # Base name.
 pure function basename (name) returning string = @{
-    basename %name
+    basename -- %name
 }
 
 # Directory name.
 pure function dirname (name) returning string = @{
-    dirname %name
+    dirname -- %name
 }
 
 # File extension.
@@ -114,12 +124,12 @@ pure function extension (name) returning string = @{
 
 # Read a file.
 function read (filename) returning string = @{
-    cat %filename
+    cat -- %filename
 }
 
 # Read a file as a list of lines.
 function readlines (filename) returning strings = @{
-    cat %filename
+    cat -- %filename
 }
 
 # Real path.