Implement +/- operators for timestamp.

doc/src/language/timestamps.md

@@ -19,9 +19,11 @@ Built-in Functions
 The following methods (defined in the [`BasicTimePackage`][packages] but excluded if using a [raw `Engine`]) operate on timestamps:
 
 | Function                      | Parameter(s)                                | Description                                              |
-| ----------------------------- | ---------------------------------- | -------------------------------------------------------- |
+| ----------------------------- | ------------------------------------------- | -------------------------------------------------------- |
 | `elapsed` method and property | _none_                                      | returns the number of seconds since the timestamp        |
-| `-` operator                  | later timestamp, earlier timestamp | returns the number of seconds between the two timestamps |
+| `-` operator                  | 1) later timestamp<br/>2) earlier timestamp | returns the number of seconds between the two timestamps |
+| `+` operator                  | number of seconds to add                    | returns a new timestamp                                  |
+| `-` operator                  | number of seconds to subtract               | returns a new timestamp                                  |
 
 
 Examples

src/packages/time_basic.rs

@@ -1,23 +1,23 @@
 #![cfg(not(feature = "no_std"))]
 
-#[cfg(feature = "no_float")]
+use super::{arithmetic::make_err as make_arithmetic_err, math_basic::MAX_INT};
-use super::{arithmetic::make_err, math_basic::MAX_INT};
 
+use crate::any::Dynamic;
 use crate::def_package;
+use crate::parser::INT;
 use crate::plugin::*;
 use crate::result::EvalAltResult;
 
 #[cfg(not(feature = "no_float"))]
 use crate::parser::FLOAT;
 
-#[cfg(feature = "no_float")]
+use crate::stdlib::boxed::Box;
-use crate::parser::INT;
 
 #[cfg(not(target_arch = "wasm32"))]
-use crate::stdlib::time::Instant;
+use crate::stdlib::time::{Duration, Instant};
 
 #[cfg(target_arch = "wasm32")]
-use instant::Instant;
+use instant::{Duration, Instant};
 
 def_package!(crate:BasicTimePackage:"Basic timing utilities.", lib, {
     // Register date/time functions
@@ -43,7 +43,7 @@ mod time_functions {
             let seconds = timestamp.elapsed().as_secs();
 
             if cfg!(not(feature = "unchecked")) && seconds > (MAX_INT as u64) {
-                Err(make_err(format!(
+                Err(make_arithmetic_err(format!(
                     "Integer overflow for timestamp.elapsed: {}",
                     seconds
                 )))
@@ -70,18 +70,18 @@ mod time_functions {
             let seconds = (ts2 - ts1).as_secs();
 
             if cfg!(not(feature = "unchecked")) && seconds > (MAX_INT as u64) {
-                Err(make_err(format!(
+                Err(make_arithmetic_err(format!(
                     "Integer overflow for timestamp duration: -{}",
                     seconds
                 )))
             } else {
-                Ok(Dynamic::from(-(seconds as INT)))
+                Ok((-(seconds as INT)).into())
             }
         } else {
             let seconds = (ts1 - ts2).as_secs();
 
             if cfg!(not(feature = "unchecked")) && seconds > (MAX_INT as u64) {
-                Err(make_err(format!(
+                Err(make_arithmetic_err(format!(
                     "Integer overflow for timestamp duration: {}",
                     seconds
                 )))
@@ -91,6 +91,103 @@ mod time_functions {
         }
     }
 
+    #[cfg(not(feature = "no_float"))]
+    pub mod float_functions {
+        #[rhai_fn(return_raw, name = "+")]
+        pub fn add(x: Instant, seconds: FLOAT) -> Result<Dynamic, Box<EvalAltResult>> {
+            if seconds < 0.0 {
+                return subtract(x, -seconds);
+            }
+
+            if cfg!(not(feature = "unchecked")) {
+                if seconds > (MAX_INT as FLOAT) {
+                    Err(make_arithmetic_err(format!(
+                        "Integer overflow for timestamp add: {}",
+                        seconds
+                    )))
+                } else {
+                    x.checked_add(Duration::from_millis((seconds * 1000.0) as u64))
+                        .ok_or_else(|| {
+                            make_arithmetic_err(format!(
+                                "Timestamp overflow when adding {} second(s)",
+                                seconds
+                            ))
+                        })
+                        .map(Into::<Dynamic>::into)
+                }
+            } else {
+                Ok((x + Duration::from_millis((seconds * 1000.0) as u64)).into())
+            }
+        }
+
+        #[rhai_fn(return_raw, name = "-")]
+        pub fn subtract(x: Instant, seconds: FLOAT) -> Result<Dynamic, Box<EvalAltResult>> {
+            if seconds < 0.0 {
+                return add(x, -seconds);
+            }
+
+            if cfg!(not(feature = "unchecked")) {
+                if seconds > (MAX_INT as FLOAT) {
+                    Err(make_arithmetic_err(format!(
+                        "Integer overflow for timestamp add: {}",
+                        seconds
+                    )))
+                } else {
+                    x.checked_sub(Duration::from_millis((seconds * 1000.0) as u64))
+                        .ok_or_else(|| {
+                            make_arithmetic_err(format!(
+                                "Timestamp overflow when adding {} second(s)",
+                                seconds
+                            ))
+                        })
+                        .map(Into::<Dynamic>::into)
+                }
+            } else {
+                Ok((x - Duration::from_millis((seconds * 1000.0) as u64)).into())
+            }
+        }
+    }
+
+    #[rhai_fn(return_raw, name = "+")]
+    pub fn add(x: Instant, seconds: INT) -> Result<Dynamic, Box<EvalAltResult>> {
+        if seconds < 0 {
+            return subtract(x, -seconds);
+        }
+
+        if cfg!(not(feature = "unchecked")) {
+            x.checked_add(Duration::from_secs(seconds as u64))
+                .ok_or_else(|| {
+                    make_arithmetic_err(format!(
+                        "Timestamp overflow when adding {} second(s)",
+                        seconds
+                    ))
+                })
+                .map(Into::<Dynamic>::into)
+        } else {
+            Ok((x + Duration::from_secs(seconds as u64)).into())
+        }
+    }
+
+    #[rhai_fn(return_raw, name = "-")]
+    pub fn subtract(x: Instant, seconds: INT) -> Result<Dynamic, Box<EvalAltResult>> {
+        if seconds < 0 {
+            return add(x, -seconds);
+        }
+
+        if cfg!(not(feature = "unchecked")) {
+            x.checked_sub(Duration::from_secs(seconds as u64))
+                .ok_or_else(|| {
+                    make_arithmetic_err(format!(
+                        "Timestamp overflow when adding {} second(s)",
+                        seconds
+                    ))
+                })
+                .map(Into::<Dynamic>::into)
+        } else {
+            Ok((x - Duration::from_secs(seconds as u64)).into())
+        }
+    }
+
     #[rhai_fn(name = "==")]
     #[inline(always)]
     pub fn eq(x: Instant, y: Instant) -> bool {

tests/time.rs

@@ -50,3 +50,60 @@ fn test_timestamp() -> Result<(), Box<EvalAltResult>> {
 
     Ok(())
 }
+
+#[test]
+fn test_timestamp_op() -> Result<(), Box<EvalAltResult>> {
+    let engine = Engine::new();
+
+    #[cfg(not(feature = "no_float"))]
+    assert!(
+        (engine.eval::<FLOAT>(
+            r#"
+                let time1 = timestamp();
+                let time2 = time1 + 123.45;
+                time2 - time1
+    "#
+        )? - 123.45)
+            .abs()
+            < 0.001
+    );
+
+    #[cfg(not(feature = "no_float"))]
+    assert!(
+        (engine.eval::<FLOAT>(
+            r#"
+                let time1 = timestamp();
+                let time2 = time1 - 123.45;
+                time1 - time2
+    "#
+        )? - 123.45)
+            .abs()
+            < 0.001
+    );
+
+    #[cfg(feature = "no_float")]
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let time1 = timestamp();
+                let time2 = time1 + 42;
+                time2 - time1
+    "#
+        )?,
+        42
+    );
+
+    #[cfg(feature = "no_float")]
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let time1 = timestamp();
+                let time2 = time1 - 42;
+                time1 - time2
+    "#
+        )?,
+        42
+    );
+
+    Ok(())
+}