Add another test for `for`. There's another one I want to add too.
Chris Pressey
4 years ago
| 1771 | 1771 | |
| 1772 | 1772 | Basic "open-faced for" loop. We'll start with the "upto" variant. |
| 1773 | 1773 | |
| 1774 | In a "for" loop, we know the exact range the loop variable takes on. | |
| 1774 | #### upward-counting variant | |
| 1775 | ||
| 1776 | Even though we do not give the starting value in the "for" construct, | |
| 1777 | we know the exact range the loop variable takes on. | |
| 1775 | 1778 | |
| 1776 | 1779 | | byte table[16] tab |
| 1777 | 1780 | | |
| 1803 | 1806 | | } |
| 1804 | 1807 | | } |
| 1805 | 1808 | ? UnmeaningfulReadError |
| 1809 | ||
| 1810 | Because routines current do not express range constraints, It may not do to take the loop variable as an input. (?) | |
| 1811 | ||
| 1812 | | byte table[16] tab | |
| 1813 | | | |
| 1814 | | define foo routine | |
| 1815 | | inputs tab, x | |
| 1816 | | trashes a, x, c, z, v, n { | |
| 1817 | | for x up to 15 { | |
| 1818 | | ld a, 0 | |
| 1819 | | } | |
| 1820 | | } | |
| 1821 | ? RangeExceededError | |
| 1806 | 1822 | |
| 1807 | 1823 | You cannot modify the loop variable in a "for" loop. |
| 1808 | 1824 | |
| 1874 | 1890 | | } |
| 1875 | 1891 | ? RangeExceededError |
| 1876 | 1892 | |
| 1893 | You can initialize something inside the loop that was uninitialized outside. | |
| 1894 | ||
| 1895 | | define main routine | |
| 1896 | | outputs x, y, n, z | |
| 1897 | | trashes c | |
| 1898 | | { | |
| 1899 | | ld x, 0 | |
| 1900 | | for x up to 15 { | |
| 1901 | | ld y, 15 | |
| 1902 | | } | |
| 1903 | | } | |
| 1904 | = ok | |
| 1905 | ||
| 1906 | But you can't UNinitialize something at the end of the loop that you need | |
| 1907 | initialized at the start of that loop. | |
| 1908 | ||
| 1909 | | define foo routine | |
| 1910 | | trashes y | |
| 1911 | | { | |
| 1912 | | } | |
| 1913 | | | |
| 1914 | | define main routine | |
| 1915 | | outputs x, y, n, z | |
| 1916 | | trashes c | |
| 1917 | | { | |
| 1918 | | ld x, 0 | |
| 1919 | | ld y, 15 | |
| 1920 | | for x up to 15 { | |
| 1921 | | inc y | |
| 1922 | | call foo | |
| 1923 | | } | |
| 1924 | | } | |
| 1925 | ? UnmeaningfulReadError: y | |
| 1926 | ||
| 1927 | #### downward-counting variant | |
| 1928 | ||
| 1877 | 1929 | In a "for" loop (downward-counting variant), we know the exact range the loop variable takes on. |
| 1878 | 1930 | |
| 1879 | 1931 | | byte table[16] tab |
| 1930 | 1982 | | } |
| 1931 | 1983 | | } |
| 1932 | 1984 | ? RangeExceededError |
| 1933 | ||
| 1934 | You can initialize something inside the loop that was uninitialized outside. | |
| 1935 | ||
| 1936 | | define main routine | |
| 1937 | | outputs x, y, n, z | |
| 1938 | | trashes c | |
| 1939 | | { | |
| 1940 | | ld x, 0 | |
| 1941 | | for x up to 15 { | |
| 1942 | | ld y, 15 | |
| 1943 | | } | |
| 1944 | | } | |
| 1945 | = ok | |
| 1946 | ||
| 1947 | But you can't UNinitialize something at the end of the loop that you need | |
| 1948 | initialized at the start of that loop. | |
| 1949 | ||
| 1950 | | define foo routine | |
| 1951 | | trashes y | |
| 1952 | | { | |
| 1953 | | } | |
| 1954 | | | |
| 1955 | | define main routine | |
| 1956 | | outputs x, y, n, z | |
| 1957 | | trashes c | |
| 1958 | | { | |
| 1959 | | ld x, 0 | |
| 1960 | | ld y, 15 | |
| 1961 | | for x up to 15 { | |
| 1962 | | inc y | |
| 1963 | | call foo | |
| 1964 | | } | |
| 1965 | | } | |
| 1966 | ? UnmeaningfulReadError: y | |
| 1967 | 1985 | |
| 1968 | 1986 | ### save ### |
| 1969 | 1987 | |