From 1f6b59bdae24b27e3f3dfcc4cd7a35d3fc91fa83 Mon Sep 17 00:00:00 2001
From: bakk <bakk@tuta.io>
Date: Tue, 1 Jun 2021 15:52:41 +0200
Subject: [PATCH] Added prod function and proper sum symbol

---
 kalk/src/interpreter.rs            | 27 ++++++++++++++++++++++-----
 kalk/src/lexer.rs                  |  1 +
 kalk/src/prelude/mod.rs            |  3 +++
 kalk_cli/src/repl.rs               |  2 ++
 kalk_web/src/KalkCalculator.svelte |  8 ++++++--
 5 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/kalk/src/interpreter.rs b/kalk/src/interpreter.rs
index 4701555..d57f77f 100644
--- a/kalk/src/interpreter.rs
+++ b/kalk/src/interpreter.rs
@@ -310,25 +310,42 @@ pub(crate) fn eval_fn_call_expr(
 
     // Special functions
     match identifier.full_name.as_ref() {
-        "sum" | "Σ" => {
+        "sum" | "Σ" | "∑" | "prod" | "∏" => {
             // Make sure exactly 3 arguments were supplied.
             if expressions.len() != 3 {
                 return Err(CalcError::IncorrectAmountOfArguments(
                     3,
-                    "sum".into(),
+                    "sum/prod".into(),
                     expressions.len(),
                 ));
             }
 
             let start = eval_expr(context, &expressions[0], "")?.to_f64() as i128;
             let end = eval_expr(context, &expressions[1], "")?.to_f64() as i128;
-            let mut sum = KalkNum::default();
+            let sum_else_prod = match identifier.full_name.as_ref() {
+                "sum" => true,
+                "Σ" => true,
+                "∑" => true,
+                "prod" => false,
+                "∏" => false,
+                _ => unreachable!(),
+            };
+            let mut sum = if sum_else_prod {
+                KalkNum::default()
+            } else {
+                KalkNum::from(1f64)
+            };
 
             for n in start..=end {
                 context.sum_n_value = Some(n);
                 let eval = eval_expr(context, &expressions[2], "")?;
-                sum.value += eval.value;
-                sum.imaginary_value += eval.imaginary_value;
+                if sum_else_prod {
+                    sum.value += eval.value;
+                    sum.imaginary_value += eval.imaginary_value;
+                } else {
+                    sum.value *= eval.value;
+                    sum.imaginary_value *= eval.imaginary_value;
+                }
             }
 
             context.sum_n_value = None;
diff --git a/kalk/src/lexer.rs b/kalk/src/lexer.rs
index f9aa5cb..54af437 100644
--- a/kalk/src/lexer.rs
+++ b/kalk/src/lexer.rs
@@ -143,6 +143,7 @@ impl<'a> Lexer<'a> {
             'τ' => build(TokenKind::Identifier, "τ", span),
             'ϕ' => build(TokenKind::Identifier, "ϕ", span),
             'Γ' => build(TokenKind::Identifier, "Γ", span),
+            '∏' => build(TokenKind::Identifier, "Γ", span),
             _ => build(TokenKind::Unknown, "", span),
         };
 
diff --git a/kalk/src/prelude/mod.rs b/kalk/src/prelude/mod.rs
index 0e2bee2..db2b75c 100644
--- a/kalk/src/prelude/mod.rs
+++ b/kalk/src/prelude/mod.rs
@@ -161,6 +161,9 @@ impl BinaryFuncInfo {
 pub fn is_prelude_func(identifier: &str) -> bool {
     identifier == "sum"
         || identifier == "Σ"
+        || identifier == "∑"
+        || identifier == "prod"
+        || identifier == "∏"
         || identifier == "integrate"
         || identifier == "integral"
         || identifier == "∫"
diff --git a/kalk_cli/src/repl.rs b/kalk_cli/src/repl.rs
index b9caf5d..3a736c8 100644
--- a/kalk_cli/src/repl.rs
+++ b/kalk_cli/src/repl.rs
@@ -115,6 +115,7 @@ lazy_static! {
         m.insert("floor", "⌊⌋");
         m.insert("gamma", "Γ");
         m.insert("sum", "Σ()");
+        m.insert("prod", "∏()");
         m.insert("integrate", "∫()");
         m.insert("integral", "∫()");
         m.insert("phi", "ϕ");
@@ -152,6 +153,7 @@ impl Completer for RLHelper {
         line.insert_str(line.pos(), elected);
         line.move_forward(match elected {
             "Σ()" => 2,
+            "∏()" => 2,
             "∫()" => 2,
             _ => 1,
         });
diff --git a/kalk_web/src/KalkCalculator.svelte b/kalk_web/src/KalkCalculator.svelte
index 5286b28..38d9cfb 100644
--- a/kalk_web/src/KalkCalculator.svelte
+++ b/kalk_web/src/KalkCalculator.svelte
@@ -33,7 +33,7 @@
         "π",
         ",",
         "%",
-        "Σ",
+        "∑",
         "⌊",
         "⌈",
         "∫",
@@ -272,7 +272,11 @@
                             break;
                         }
                         case "sum": {
-                            newSubstring = "Σ";
+                            newSubstring = "∑";
+                            break;
+                        }
+                        case "prod": {
+                            newSubstring = "∏";
                             break;
                         }
                         case "integrate": {