Documentation for arithmetic operations (+, -, *, /, ^)

The documentation for the basic operations was not written.

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

doc/commands/arithmetic.md

@@ -1,3 +1,104 @@
+# Arithmetic
+
+## + (add)
+
+Add two values.
+
+* For integer, fractional, decimal or complex numbers, this performs the
+  expected numerical addition. For example, `1 2 +` is `3`.
+* For equations and symbols, build a sum, eliminating zero additions if
+  [autosimplify](#autosimplify) is active.
+* For lists, concatenate lists, or add objets to a list. For example, `{ A } { B
+  } +` is `{ A B }`, and `{ A B C } "D" +` is `{ A B C "D" }`.
+* For text, concatenate text, or concatenate the text representation of an
+  object to an existing text. For example `"X" "Y" + ` gives `"XY"`, and
+  `"X=" 1 +` gives `"X=1"`.
+
+## - (sub)
+
+Subtract two values
+
+* For integer, fractional, decimal or complex numbers, this performs the
+  expected numerical subtraction. For example, `1 2 -` is `-1`.
+* For equations and symbols, build a difference, eliminating subtraction of 0 if
+  [autosimplify](#autosimplify) is active.
+
+## + (add)
+
+Add two values.
+
+* For integer, fractional, decimal or complex numbers, this performs the
+  expected numerical addition. For example, `1 2 +` is `3`.
+* For vectors and matrices, add individual elements. For example,
+  `[ 1 2 3 ] [ 4 5 6 ] +` is `[ 5 7 9 ]`.
+* For equations and symbols, build a sum, eliminating zero additions
+  when [autosimplify](#autosimplify) is active.
+* For lists, concatenate lists, or add objets to a list. For example, `{ A } { B
+  } +` is `{ A B }`, and `{ A B C } "D" +` is `{ A B C "D" }`.
+* For text, concatenate text, or concatenate the text representation of an
+  object to an existing text. For example `"X" "Y" + ` gives `"XY"`, and
+  `"X=" 1 +` gives `"X=1"`.
+
+## - (sub)
+
+Subtract two values
+
+* For integer, fractional, decimal or complex numbers, this performs the
+  expected numerical subtraction. For example, `1 2 -` is `-1`.
+* For vectors and matrices, subtract individual elements. For example,
+  `[ 1 2 3 ] [ 1 3 0 ] -` is `[ 0 -1 3 ]`.
+* For equations and symbols, build a difference, eliminating subtraction of 0
+  when [autosimplify](#autosimplify) is active.
+
+
+## × (*, mul)
+
+Multiply two values.
+
+* For integer, fractional, decimal or complex numbers, this performs the
+  expected numerical multiplication. For example, `3 2 *` is `6`.
+* For vectors, multiply individual elements (this is a deviation from HP48).
+  For example, `[ 1 2 3 ] [ 4 5 6 ] +` is `[ 4 10 18 ]`.
+* For matrices, perform a matrix multiplication.
+* For a matrix and a vector, apply the matrix to the vector.
+* For equations and symbols, build a product, eliminating mulitplication by 1
+  or 0 when [autosimplify](#autosimplify) is active.
+* For a list and a positive integer, repeat the list For example, `{ A } 3 *`
+  is `{ A A A }`.
+* For a text and a positive integer, repeat the text. For example `"X" 3 * `
+  gives `"XXX"`.
+
+
+## ÷ (/, div)
+
+Divide two values two values
+
+* For integer, build a fraction. For example `1 7 /` gives `1/7`.
+* For fractional, decimal or complex numbers, this performs the
+  expected numerical division. For example, `1. 2. /` is `0.5`.
+* For vectors, divide individual elements. For example,
+  `[ 1 2 3 ] [ 3 2 1 ] /` is `[ 1/3 1 3 ]`.
+* For equations and symbols, build a ratio, eliminating division by one
+  and division of 0 when [autosimplify](#autosimplify) is active.
+
+
+## ↑ (^, pow)
+
+Raise to the power
+
+* For integer, fractional, decimal or complex numbers, this raises the
+  value in level 2 to the value in level 1. For example, `2 3 ↑` is `8`.
+* For vectors, raise individual elements in the first vector to the power of the
+  corresponding element in the second vector.
+* For equations and synbols, build an expression, eliminating special cases
+  when [autosimplify](#autosimplify) is active.
+
+
+## xroot
+
+Raise to the inverse power. `X Y xroot` is equivalent to `X Y inv pow`.
+
+
 # Integer arithmetic and polynomials
 
 ## SETPREC

src/user_interface.cc

@@ -3387,7 +3387,7 @@ static const byte defaultSecondShiftedCommand[2*user_interface::NUM_KEYS] =
 //   All the default assigned commands fit in one or two bytes
 {
     OP2BYTES(KEY_SIGMA, menu::ID_MainMenu),
-    OP2BYTES(KEY_INV,   0),
+    OP2BYTES(KEY_INV,   command::ID_xroot),
     OP2BYTES(KEY_SQRT,  menu::ID_RealMenu),
     OP2BYTES(KEY_LOG,   function::ID_expm1),
     OP2BYTES(KEY_LN,    function::ID_log1p),