tests: expand testing of augmented assignment operators (#70)

Add some more tests for augmented assignment operators, and remove some
existing ones that had similar coverage.

assignops.c4m was similar to basic10.c4m:

    """
    Basic test of augmented assignment.
    """
    """
    $output:
    45
    """

    x = 0

    for i in 0 to 10 {
      x  += i
    }

    print(x)

The grammar specifies the augmented assignment operators here:

    assign       ::= expression assignmentOp expression EOS
    assignmentOp ::= ':' | '=' | '+=' | '-=' | '*=' | '/=' | '|=' | '&=' | '^=' | '>>=' | '<<='

Note that commit b4fdc8e (2024-07-03, "Reworking of lists, etc")
changed the behavior of the /= operator so that:

- For division by zero, SIGFPE is no longer produced.

- For division by a negative number, the result is now correct.

Refs: #55
Refs: #57
Refs: #71

tests/assignops_all.c4m

@@ -0,0 +1,44 @@
+"""
+Basic test of every augmented assignment operator.
+"""
+"""
+$output:
+3
+-2
+-12
+6
+7
+5
+13
+3
+6
+"""
+
+x = 2
+
+x += 1
+print(x)
+
+x -= 5
+print(x)
+
+x *= 6
+print(x)
+
+x /= -2
+print(x)
+
+x |= 7
+print(x)
+
+x &= 13
+print(x)
+
+x ^= 8
+print(x)
+
+x >>= 2
+print(x)
+
+x <<= 1
+print(x)

tests/assignops_divide.c4m

@@ -0,0 +1,32 @@
+"""
+Basic test of augmented assignment operator: /=
+"""
+"""
+$output:
+12
+6
+-6
+-3
+3
+"""
+
+x = 12
+
+x /= 1
+print(x)
+
+x /= 2
+print(x)
+
+x /= -1
+print(x)
+
+x /= 2
+print(x)
+
+x /= -1
+print(x)
+
+# TODO: remove this later. See basic25.c4m.
+x /= 0
+print(x)

tests/assignops_multiply.c4m

@@ -0,0 +1,32 @@
+"""
+Basic test of augmented assignment operator: *=
+"""
+"""
+$output:
+3
+6
+-6
+-12
+24
+0
+"""
+
+x = 3
+
+x *= 1
+print(x)
+
+x *= 2
+print(x)
+
+x *= -1
+print(x)
+
+x *= 2
+print(x)
+
+x *= -2
+print(x)
+
+x *= 0
+print(x)

tests/assignops_shift_left.c4m

@@ -0,0 +1,52 @@
+"""
+Basic test of augmented assignment operator: <<=
+"""
+"""
+$output:
+0
+0
+1
+2
+8
+4611686018427387904
+-1
+-2
+-2305843009213693952
+-4611686018427387904
+"""
+
+x = 0
+
+x <<= 0
+print(x)
+
+x <<= 1
+print(x)
+
+x = 1
+
+x <<= 0
+print(x)
+
+x <<= 1
+print(x)
+
+x <<= 2
+print(x)
+
+x <<= 59
+print(x)
+
+x = -1
+
+x <<= 0
+print(x)
+
+x <<= 1
+print(x)
+
+x <<= 60
+print(x)
+
+x <<= 1
+print(x)

tests/assignops_shift_right.c4m

@@ -0,0 +1,42 @@
+"""
+Basic test of augmented assignment operator: >>=
+"""
+"""
+$output:
+9223372036854775807
+9223372036854775807
+4611686018427387903
+15
+7
+1
+0
+0
+0
+"""
+
+x = 0x7fffffffffffffff
+print(x)
+
+x >>= 0
+print(x)
+
+x >>= 1
+print(x)
+
+x >>= 58
+print(x)
+
+x >>= 1
+print(x)
+
+x >>= 2
+print(x)
+
+x >>= 1
+print(x)
+
+x >>= 0
+print(x)
+
+x >>= 1
+print(x)

tests/assignops_xor.c4m

@@ -0,0 +1,32 @@
+"""
+Basic test of augmented assignment operator: ^=
+"""
+"""
+$output:
+2
+0
+-2
+-4
+-4
+3
+"""
+
+x = 3
+
+x ^= 1
+print(x)
+
+x ^= 2
+print(x)
+
+x ^= -2
+print(x)
+
+x ^= 2
+print(x)
+
+x ^= 0
+print(x)
+
+x ^= -1
+print(x)