all tasks

Task/Stack/Tcl/stack-1.tcl

@@ -0,0 +1,31 @@
+proc push {stackvar value} {
+    upvar 1 $stackvar stack
+    lappend stack $value
+}
+proc pop {stackvar} {
+    upvar 1 $stackvar stack
+    set value [lindex $stack end]
+    set stack [lrange $stack 0 end-1]
+    return $value
+}
+proc size {stackvar} {
+    upvar 1 $stackvar stack
+    llength $stack
+}
+proc empty {stackvar} {
+    upvar 1 $stackvar stack
+    expr {[size stack] == 0}
+}
+proc peek {stackvar} {
+    upvar 1 $stackvar stack
+    lindex $stack end
+}
+
+set S [list]
+empty S ;# ==> 1 (true)
+push S foo
+empty S ;# ==> 0 (false)
+push S bar
+peek S ;# ==> bar
+pop S ;# ==> bar
+peek S ;# ==> foo

Task/Stack/Tcl/stack-2.tcl

@@ -0,0 +1,10 @@
+package require struct::stack
+struct::stack S
+S size ;# ==> 0
+S push a b c d e
+S size ;# ==> 5
+S peek ;# ==> e
+S pop ;# ==> e
+S peek ;# ==> d
+S pop 4 ;# ==> d c b a
+S size ;# ==> 0